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Two types of hibiscus that commonly brighten gardens and yards in the United States are the hardy hibiscus (Hibiscus moscheutos), USDA plant hardiness zones 4 through 9, and the tropical hibiscus (Hibiscus rosa-sinensis), USDA zones 9 through 10. Considered showstoppers for their oversized, vibrantly colored blooms, these plants are also known for being relatively easy to grow. Although both types are susceptible to damage by insects, many of these pests can be effectively controlled or eliminated by using a homemade insecticidal soap.

Common Soft-Bodied Hibiscus Pests

Both tropical and hardy hibiscus attract mealybugs and spider mites. Aphids, scales and thrips prefer tropical hibiscus, whereas whiteflies and hibiscus sawfly larvae often plague the hardy plants. Insecticidal soaps work on soft-bodied insects such as these by removing their protective covering, which causes them to dehydrate and die. The soap is less effective on the eggs of these insects and on hard-bodied pests such as grasshoppers.

When identifying an infestation, you'll want to look at the undersides of the leaves as well as the tops. A magnifying glass will help you spot the tiny invaders:

Aphids have pear-shaped bodies that are covered with a waxy white or gray substance.

Scales are circular with no separate head or distinctive body parts.

Mealybugs have segmented bodies and, like aphids, are covered by a waxy exterior.

Thrips are elongated and slender and have narrow wings.

Spider mites are outfitted with eight legs, oval bodies and two red eyes.

Whiteflies are triangular in shape and group together in clusters.

Hibiscus sawfly larvae are green in color with elongated bodies.

Making the Insecticidal Soap

Start off with a gallon of pure water. Bottled or distilled water performs better than tap water, which often contains minerals that can make insecticidal soap less effective. Add 2 1/2 to 5 tablespoons of mild liquid dish soap or hand soap to the water. Mix the two ingredients together in a garden sprayer and you're ready to begin the application.

Applying the Insecticidal Soap

While hibiscus plants aren't known for being sensitive to insecticidal soap, you may still wish to spray it on a small test area first. Return to the plant 24 hours later and check to ensure that the test area is unaffected. If there's no damage, it's safe to treat the entire plant.

Spray both the tops and bottoms of the hibiscus plant's leaves liberally with insecticidal soap either early in the morning or late in the afternoon. This time of day is best, as the noonday sun will dry out the solution much faster, decreasing the number of insects that are killed. The insects must come in direct contact with the insecticidal soap, so make sure you look for and target the pests when applying the solution. Repeat the procedure every four to seven days until you no longer spot any insects on your hibiscus plants.

Advantages of Insecticidal Soap

Chemical pesticides may be effective in treating insects that frequent hibiscus plants, but they also have the potential to harm other animals. Insecticidal soap is less toxic than commercial pesticides and is not a threat to beneficial insects, birds and pets. It's also inexpensive and easy to make at home.

Tip

You can also purchase a commercial insecticidal soap at your local gardening center. When going this route, carefully follow the product label for application, amount and timing details.

Warning

It's important to only use insecticidal soap when temperatures are below 90 degrees Fahrenheit, as high heat and humidity may cause the plant to become more sensitive.